This invention deals with treatment of disorders of skin which appear to be associated with factors that influence the balance of thymus-derived (T) immune cells known as Th1 and Th2. These T cells are identified by their cytokine secretion phenotype. A common feature of treatment is the use of compounds prepared from M. vaccae which have immunomodulating properties that alter the balance of activities of these T cells as well as other immune cells.
Psoriasis is a common, chronic inflammatory skin disease which can be associated with various forms of arthritis in a minority of patients. The defect in psoriasis appears to be overly rapid growth of keratinocytes and shedding of scales from the skin surface. Drug therapy is directed at slowing down this process. The disease may become manifest at any age. Spontaneous remission is relatively rare, and life-long treatment is usually necessary. Psoriasis produces chronic, scaling red patches on the skin surface. Psoriasis is a very visible disease, it frequently affects the face, scalp, trunk and limbs. The disease is emotionally and physically debilitating for the patient, detracting significantly from the quality of life. Between one and three million individuals in the United States have psoriasis with nearly a quarter million new cases occurring each year. Conservative estimates place the costs of psoriasis care in the United States currently at $248 million a year.
There are two major hypotheses concerning the pathogenesis of psoriasis. The first is that genetic factors determine abnormal proliferation of epidermal keratinocytes. The cells no longer respond normally to external stimuli such as those involved in maintaining epidermal homeostasis. Abnormal expression of cell membrane cytokine receptors or abnormal transmembrane signal transduction might underlie cell hyperproliferation. Inflammation associated with psoriasis is secondary to the release of pro-inflammatory molecules from hyperproliferative keratinocytes.
A second hypothesis is that T cells interacting with antigen-presenting cells in skin release pro-inflammatory and keratinocyte-stimulating cytokines (Hancock, G. E. et al., J. Exp. Med. 168:1395-1402, 1988). Only T cells of genetically predetermined individuals possess the capacity to be activated under such circumstances. The keratinocytes themselves may be the antigen-presenting cell. The cellular infiltrate in psoriatic lesions show an influx of CD4+ T cells and, more prominently, CD8.sup.+ T cells (Bos, J. D. et al., Arch. Dermatol. Res. 281:23-3, 1989; Baker, B. S., Br. J Dermatol. 110:555-564, 1984).
As the majority (90%) of psoriasis patients have limited forms of the disease, topical treatments which include dithranol, tar preparations, corticosteroids and the recently introduced vitamin D3 analogues (calcipotriol, calcitriol) can be used. A minority (10%) of psoriasis patients have a more serious condition, for which a number of systemic therapeutic modalities are available. Specific systemic therapies include UVB, PUVA, methotrexate, vitamin A derivatives (acitretin) and immuno-suppressants such as Cyclosporin A. The effectiveness of Cyclosporin and FK-506 for treating psoriasis provides support for the T cell hypothesis as the prime cause of the disease (Bos, J. D. et al., Lancet II: 1500-1502, 1989; Ackerman, C. et al., J. Invest. Dermatol. 96:536 [abstract], 1991).
Atopic dermatitis is a chronic pruritic inflammatory skin disease which usually occurs in families with an hereditary predisposition for various allergic disorders such as allergic rhinitis and asthma. Atopic dermatitis occurs in approximately 10% of the general population. The main symptoms are dry skin, dermatitis (eczema) localised mainly in the face, neck and on the flexor sides and folds of the extremities accompanied by severe itching. It typically starts within the first two years of life. In about 90% of the patients this skin disease disappears during childhood but the symptoms can continue into adult life. It is one of the commonest forms of dermatitis world-wide. It is generally accepted that in atopy and in atopic dermatitis, a T cell abnormality is primary and that the dysfunction of T cells which normally regulate the production of IgE is responsible for the excessive production of this immunoglobulin.
Allergic contact dermatitis is a common non-infectious inflammatory disorder of the skin. In contact dermatitis, immunological reactions cannot develop until the body has become sensitised to a particular antigen. Subsequent exposure of the skin to the antigen and the recognition of these antigens by T cells result in the release of various cytokines, proliferation and recruitment of T cells and finally in dermatitis (eczema).
Only a small proportion of the T cells in a lesion of allergic contact dermatitis are specific for the relevant antigen. Activated T cells probably migrate to the sites of inflammation regardless of antigen-specificity. Delayed-type hypersensitivity can only be transferred by T cells (CD4.sup.+ cells) sharing the MHC class II antigens. The `response` to contact allergens can be transferred by T cells sharing either MHC class I (CD8.sup.+ cells) or class II (CD4.sup.+ cells) molecules (Sunday, M. E. et al., J. Immunol. 125:1601-1605, 1980). Keratinocytes can produce interleukin-1 which can facilitate the antigen presentation to T cells. The expression of the surface antigen intercellular adhesion molecule-1 (ICAM-1) is induced both on keratinocytes and endothelium by the cytokines tumor necrosis factor (TNF) and interferon-gamma (IFN-.gamma.).
If the causes can be identified, removal alone will cure allergic contact dermatitis. During active inflammation, topical corticosteroids are useful. An inhibitory effect of cyclosporin has been observed in delayed-type hypersensitivity on the pro-inflammatory function(s) of primed T cells in vitro (Shidani, B. et al., Eur. J Immunol. 14:314-318, 1984). The inhibitory effect of cyclosporin on the early phase of T cell activation in mice has also been reported (Milon, G. et al., Ann. Immunol. (Inst. Pasteur) 135d:237-245, 1984).
Alopecia areata is a common hair disease, which accounts for about 2% of the consultations at dermatological outpatient clinics in the United States. The hallmark of this disease is the formation of well-circumscribed round or oval patches of non-scarring alopecia which may be located in any hairy area of the body. The disease may develop at any age. The onset is usually sudden and the clinical course is varied.
At present, it is not possible to attribute all or indeed any case of alopecia areata to a single cause (Rook, A. and Dawber, R, Diseases of the Hair and Scalp; Blackwell Scientific Publications 1982: 272-30). There are many factors that appear to be involved. These include genetic factors, atopy, association with disorders of supposed autoimmune etiology, Down's syndrome and emotional stress. The prevalence of atopy in patients with alopecia areata is increased. There is evidence that alopecia areata is an autoimmune disease. This evidence is based on consistent histopathological findings of a lymphocytic T cell infiltrate in and around the hair follicles with increased numbers of Langerhans cells, the observation that alopecia areata will respond to treatment with immunomodulating agents, and that there is a statistically significant association between alopecia areata and a wide variety of autoimmune diseases (Mitchell, A. J. et al., J. Am. Acad Dermatol. 11:763-775, 1984).
Immunophenotyping studies on scalp biopsy specimens shows expression of HLA-DR on epithelial cells in the presumptive cortex and hair follicles of active lesions of alopecia areata, as well as a T cell infiltration with a high proportion of helper/inducer T cells in and around the hair follicles, increased numbers of Langerhans cells and the expression of ICAM-1 (Messenger, A. G. et al., J. Invest. Dermatol. 85:569-576, 1985; Gupta, A. K. et al., J. Am. Acad. Dermatol. 22:242-250, 1990).
The large variety of therapeutic modalities in alopecia areata can be divided into four categories: (i) non-specific topical irritants; (ii) `immune modulators` such as systemic corticosteroids and PUVA; (iii) `immune enhancers` such as contact dermatitis inducers, cyclosporin and inosiplex; and (iv) drugs of unknown action such as minoxidil (Dawber, R. P. R. et al., Textbook of Dermatology, Blackwell Scientific Publications, 5.sup.th Ed, 1982:2533-2638). Non-specific topical irritants such as dithranol may work through as yet unidentified mechanisms rather than local irritation in eliciting regrowth of hair. Topical corticosteroids may be effective but prolonged therapy is often necessary. Intralesional steroids have proved to be more effective but their use is limited to circumscribed patches of less active disease or to maintain regrowth of the eyebrows in alopecia totalis. Photochemotherapy has proved to be effective, possibly by changing functional subpopulations of T cells. Topical immunotherapy by means of induction and maintenance of allergic contact dermatitis on the scalp may result in hair regrowth in as many as 70% of the patients with alopecia areata. Diphencyprone is a potent sensitiser free from mutagenic activity. Oral cyclosporin can be effective in the short term (Gupta, A. K. et al., J. Am. Acad. Dermatol. 22:242-250, 1990). Inosiplex, an immunostimulant, has been used with apparent effectiveness in an open trial. Topical 5% minoxidil solution has been reported to be able to induce some hair growth in patients with alopecia areata. The mechanism of action is unclear.
Carcinomas of the skin are a major public health problem because of their frequency and the disability and disfigurement that they cause. Carcinoma of the skin is principally seen in individuals in their prime of life, especially in fair skinned individuals exposed to large amounts of sunlight. The annual cost of treatment and time loss from work exceeds $250 million dollars a year in the United States alone. The three major types--basal cell cancer, squamous cell cancer, and melanoma--are clearly related to sunlight exposure.
Basal cell carcinomas are epithelial tumours of the skin. They appear predominantly on exposed areas of the skin. In a recent Australian study, the incidence of basal cell carcinomas was 652 new cases per year per 100,000 of the population. This compares with 160 cases of squamous cell carcinoma or 19 of malignant melanoma (Giles, G. et al., Br. Med J. 296:13-17, 1988). Basal cell carcinomas are the most common of all cancers. Lesions are usually surgically excised. Alternate treatments include retinoids, 5-fluorouracil, cryotherapy and radiotherapy. Alpha or gamma interferon have also been shown to be effective in the treatment of basal cell carcinomas, providing a valuable alternative to patients unsuitable for surgery or seeking to avoid surgical scars (Cornell et al., J. Am. Acad. Dermatol. 23:694-700, 1990; Edwards, L. et al., J. Am. Acad. Dermatol. 22:496-500, 1990).
Squamous cell carcinoma (SCC) is the second most common cutaneous malignancy, and its frequency is increasing. There are an increasing number of advanced and metastatic cases related to a number of underlying factors. Currently, metastatic SCC contributes to over 2000 deaths per year in the United States; the 5 year survival rate is 35%, with 90% of the metastases occurring by 3 years. Metastasis almost always occurs at the first lymphatic drainage station. The need for medical therapy for advanced cases is clear. A successful medical therapy for primary SCC of the skin would obviate the need for surgical excision with its potential for scarring and other side effects. This development may be especially desirable for facial lesions.
Because of their antiproliferative and immunomodulating effects in vitro, interferons (IFNs) have also been used in the treatment of melanoma (Kirkwood, J. M. et al., J. Invest. Dermatol. 95:180S-4S, 1990). Response rates achieved with systemic IFN-.alpha., in either high or low dose, in metastatic melanoma were in the range 5-30%. Recently, encouraging results (30% response) were obtained with a combination of IFN-.alpha. and DTIC. Preliminary observations indicate a beneficial effect of IFN-.alpha. in an adjuvant setting in patients with high risk melanoma. Despite the low efficacy of IFN monotherapy in metastatic disease, several randomised prospective studies are now being performed with IFNs as an adjuvant or in combination with chemotherapy (McLeod, G. R. et al., J. Invest. Dermatol. 95:185S-7S, 1990; Ho, V. C. et al., J. Invest. Dermatol. 22:159-76, 1990).
Of all the available therapies for treating cutaneous viral lesions, only interferon possesses a specific antiviral mode of action, by reproducing the body's immune response to infection. Interferon treatment cannot eradicate the viruses however, although it may help with some manifestations of the infection. Interferon treatment is also associated with systemic adverse effects, requires multiple injections into each single wart and has a significant economic cost (Kraus, S. J. et al., Review of Infectious Diseases 2(6):S620-S632, 1990; Frazer, I. H., Current Opinion in Immunology 8(4):484-491, 1996).
Many compositions have been developed for topical application to treat skin disorders. Such topical treatments generally have limited beneficial effects. International Patent Publication WO 91/02542 discloses treatment of chronic inflammatory disorders in which a patient demonstrates an abnormally high release of IL-6 and/or TNF or in which the patient's IgG shows an abnormally high proportion of agalactosyl IgG. Among the disorders mentioned in this publication are psoriasis, rheumatoid arthritis, mycobacterial disease, Crohn's disease, primary biliary cirrhosis, sarcoidosis, ulcerative colitis, systemic lupus erythematosus, multiple sclerosis, Guillain-Barre syndrome, primary diabetes mellitus, and some aspects of graft rejection. The therapeutic agent preferably comprises autoclaved M. vaccae administered by injection in a single dose. This publication does not disclose any clinical results.
Several other patents and publications disclose treatment of various conditions by administering mycobacteria, including M. vaccae, or certain mycobacterial fractions. U.S. Pat. No. 4,716,038 discloses diagnosis of, vaccination against and treatment of autoimmune diseases of various types, including arthritic diseases, by administering mycobacteria, including M. vaccae. U.S. Pat. No. 4,724,144 discloses an immunotherapeutic agent comprising antigenic material derived from M. vaccae for treatment of mycobacterial diseases, especially tuberculosis and leprosy, and as an adjuvant to chemotherapy. International Patent Publication WO 91/01751 discloses the use of antigenic and/or immunoregulatory material from M. vaccae as an immunoprophylactic to delay and/or prevent the onset of AIDS. International Patent Publication WO 94/06466 discloses the use of antigenic and/or immunoregulatory material derived from M. vaccae for therapy of HIV infection, with or without AIDS and with or without associated tuberculosis.
U.S. Pat. No. 5,599,545 discloses the use of mycobacteria, especially whole, inactivated M. vaccae, as an adjuvant for administration with antigens which are not endogenous to M. vaccae. This publication theorises that the beneficial effect as an adjuvant may be due to heat shock protein 65 (hsp 65). International Patent Publication WO 92/08484 discloses the use of antigenic and/or immunoregulatory material derived from M. vaccae for the treatment of uveitis. International Patent Publication WO 93/16727 discloses the use of antigenic and/or immunoregulatory material derived from M. vaccae for the treatment of mental diseases associated with an autoimmune reaction initiated by an infection. International Patent Publication WO 95/26742 discloses the use of antigenic and/or immunoregulatory material derived from M. vaccae for delaying or preventing the growth or spread of tumors.
M. vaccae is apparently unique among known mycobacterial species in that heat-killed preparations retain vaccine and immunotherapeutic properties. For example, M. bovis-BCG vaccines, used for vaccination against tuberculosis, employ live strains. Heat-killed M. bovis BCG and M. tuberculosis have no protective properties when employed in vaccines. A number of compounds have been isolated from a range of mycobacterial species which have adjuvant properties. The effect of such adjuvants is essentially to stimulate a particular immune response mechanism against an antigen from another species.
There are two general classes of compounds which have been isolated from mycobacterial species that exhibit adjuvant properties. The first are water soluble wax D fractions (R. G. White, I. Bemstock, R. G. S. Johns and E. Lederer, Immunology, 1:54, 1958; U.S. Pat. No. 4,036,953). The second are muramyl dipeptide-based substances (N-acetyl glucosamine and N-glycolymuramic acid in approximately equimolar amounts) as described in U.S. Pat. Nos. 3,956,481 and 4,036,953. These compounds differ from the delipidated and deglycolipidated M. vaccae (DD-M. vaccae) of the present invention in the following aspects of their composition:
1. They are water-soluble agents, whereas DD-M. vaccae is insoluble in aqueous solutions. PA1 2. They consist of a range of small oligomers of the mycobacterial cell wall unit, either extracted from bacteria by various solvents, or digested from the cell wall by an enzyme. In contrast, DD-M. vaccae contains highly polymerised cell wall. PA1 3. All protein has been removed from their preparations by digestion with proteolytic enzymes. The only constituents of their preparations are the components of the cell wall peptidoglycan structure, namely alanine, glutamic acid, diaminopimelic acid, N-acetyl glucosamine, and N-glycolylmuramic acid. In contrast, DD-M. vaccae contains 50% w/w protein, comprising a number of distinct protein species.
There thus remains a need in the art for effective compositions and methods for the treatment of skin disorders that are inexpensive and cause few undesirable side effects.